DSpace at VNU: Measurement of the Lambda(0)(b), Xi(-)(b), and Omega(-)(b) Baryon Masses tài liệu, giáo án, bài giảng , l...
Published for SISSA by Springer Received: April 11, 2013 Accepted: May 15, 2013 Published: May 29, 2013 The LHCb collaboration E-mail: schunem@lal.in2p3.fr Abstract: The branching fraction of the rare decay B → K ∗0 e+ e− in the dilepton mass region from 30 to 1000 MeV/c2 has been measured by the LHCb experiment, using pp collision data, corresponding to an integrated luminosity of 1.0 fb−1 , at a centre-of-mass energy of TeV The decay mode B → J/ψ (e+ e− )K ∗0 is utilized as a normalization channel The branching fraction B(B → K ∗0 e+ e− ) is measured to be B(B → K ∗0 e+ e− )30−1000 MeV/c = (3.1 +0.9 −0.8 +0.2 −0.3 ± 0.2) × 10−7 , where the first error is statistical, the second is systematic, and the third comes from the uncertainties on the B → J/ψ K ∗0 and J/ψ → e+ e− branching fractions Keywords: Rare decay, Hadron-Hadron Scattering, Branching fraction, B physics, Flavour Changing Neutral Currents ArXiv ePrint: 1304.3035 Open Access, Copyright CERN, for the benefit of the LHCb collaboration doi:10.1007/JHEP05(2013)159 JHEP05(2013)159 Measurement of the B → K ∗0e+e− branching fraction at low dilepton mass Contents The LHCb detector, dataset and analysis strategy Selection and backgrounds Fitting procedure Results Systematic uncertainties Summary 10 The LHCb collaboration 14 Introduction The b → sγ transition proceeds through flavour changing neutral currents, and thus is sensitive to the effects of physics beyond the Standard Model (BSM) Although the branching fraction of the B → K ∗0 γ decay has been measured [1–3] to be consistent with the Standard Model (SM) prediction [4], BSM effects could still be present and detectable through more detailed studies of the decay process In particular, in the SM the photon helicity is predominantly left-handed, with a small right-handed current arising from long distance effects and from the non-zero value of the ratio of the s-quark mass to the b-quark mass Information on the photon polarisation can be obtained with an angular analysis of the B → K ∗0 + − decay ( = e, µ) in the low dilepton invariant mass squared (q ) region where the photon contribution dominates The inclusion of charge-conjugate modes is implied throughout the paper The low q region also has the benefit of reduced theoretical uncertainties due to long distance contributions compared to the full q region [5] The more precise SM prediction allows for increased sensitivity to contributions from BSM In the low q interval there is a contribution from B → K ∗0 V (V → + − ) where V is one of the vector resonances ρ, ω or φ; however this contribution has been calculated to be at most 1% [6] The diagrams contributing to the B → K ∗0 e+ e− decay are shown in figure With the LHCb detector, the B → K ∗0 + − analysis can be carried out using either muons [7] or electrons Experimentally, the decay with muons in the final state produces a much higher yield per unit integrated luminosity than electrons, primarily due to the clean trigger signature In addition, the much smaller bremsstrahlung radiation leads to better momentum resolution, allowing a more efficient selection On the other hand, the –1– JHEP05(2013)159 Introduction B0 d u ¯ /¯ c/¯t ¯ b ¯s K∗0 B0 ¯ b u ¯ /¯ c/¯t e+ W d W+ ¯s K∗0 e+ + γ/Z0 γ/Z0 e− B0 e− W+ νe ¯s K∗0 W− e− e+ Figure Dominant Standard Model diagrams contributing to the decay B → K ∗0 e+ e− B → K ∗0 e+ e− decay probes lower dilepton invariant masses, thus providing greater sensitivity to the photon polarisation [5] Furthermore, the formalism is greatly simplified due to the negligible lepton mass [8] It is therefore interesting to carry out an angular analysis of the decay B → K ∗0 e+ e− in the region where the dilepton mass is less than 1000 MeV/c2 The lower limit is set to 30 MeV/c2 since below this value the sensitivity for the angular analysis decreases because of a degradation in the precision of the orientation of the e+ e− decay plane due to multiple scattering Furthermore, the contamination from the B → K ∗0 γ decay, with the photon converting into an e+ e− pair in the detector material, increases significantly as q → The first step towards performing the angular analysis is to measure the branching fraction in this very low dilepton invariant mass region Indeed, even if there is no doubt about the existence of this decay, no clear B → K ∗0 e+ e− signal has been observed in this region and therefore the partial branching fraction is unknown The only experiments to have observed B → K ∗0 e+ e− to date are BaBar [9] and Belle [10], which have collected about 30 B → K ∗0 + − events each in the region q < GeV2/c4 , summing over electron and muon final states The LHCb detector, dataset and analysis strategy The study reported here is based on pp collision data, corresponding to an integrated luminosity of 1.0 fb−1 , collected at the Large Hadron Collider (LHC) with the LHCb detector [11] at a centre-of-mass energy of TeV during 2011 The LHCb detector is a single-arm forward spectrometer covering the pseudorapidity range < η < 5, designed for the study of particles containing b or c quarks It includes a high precision tracking system consisting of a silicon-strip vertex detector (VELO) surrounding the pp interaction region, a large-area silicon-strip detector located upstream of a dipole magnet with a bending power –2– JHEP05(2013)159 d u ¯ /¯ c/¯t ¯ b Selection and backgrounds The candidate selection is divided into three steps: a loose selection, a multivariate algorithm to suppress the combinatorial background, and additional selection criteria to remove specific backgrounds Candidate K ∗0 mesons are reconstructed in the K ∗0 → K + π − mode The pT of the charged K (π) mesons must be larger than 400 (300) MeV/c Particle identification (PID) –3– JHEP05(2013)159 of about Tm, and three stations of silicon-strip detectors and straw drift tubes placed downstream The combined tracking system has momentum resolution (∆p/p) that varies from 0.4% at GeV/c to 0.6% at 100 GeV/c, and impact parameter (IP) resolution of 20 µm for tracks with high transverse momentum (pT ) Charged hadrons are identified using two ring-imaging Cherenkov detectors Photon, electron and hadron candidates are identified by a calorimeter system consisting of scintillating-pad (SPD) and preshower (PS) detectors, an electromagnetic calorimeter (ECAL) and a hadronic calorimeter Muons are identified by a system composed of alternating layers of iron and multiwire proportional chambers The trigger [12] consists of a hardware stage, based on information from the calorimeter and muon systems, followed by a software stage which applies a full event reconstruction For signal candidates to be considered in this analysis, at least one of the electrons from the B → K ∗0 e+ e− decay must pass the hardware electron trigger, or the hardware trigger must be satisfied independently of any of the daughters of the signal B candidate (usually triggering on the other b-hadron in the event) The hardware electron trigger requires the presence of an ECAL cluster with a transverse energy greater than 2.5 GeV An energy deposit is also required in one of the PS cells in front of the ECAL cluster, where the threshold corresponds to the energy that would be deposited by the passage of five minimum ionising particles Finally, at least one SPD hit is required among the SPD cells in front of the cluster The software trigger requires a two-, three- or four-track secondary vertex with a high sum of the pT of the tracks and a significant displacement from the primary pp interaction vertices (PVs) At least one track should have pT > 1.7 GeV/c and IP χ2 with respect to the primary interaction greater than 16 The IP χ2 is defined as the difference between the χ2 of the PV reconstructed with and without the considered track A multivariate algorithm is used for the identification of secondary vertices consistent with the decay of a b-hadron The strategy of the analysis is to measure a ratio of branching fractions in which most of the potentially large systematic uncertainties cancel The decay B → J/ψ (e+ e− )K ∗0 is used as normalization mode, since it has the same final state as the B → K ∗0 e+ e− decay and has a well measured branching fraction [13, 14], approximately 300 times larger than B(B → K ∗0 e+ e− ) in the e+ e− invariant mass range 30 to 1000 MeV/c2 Selection efficiencies are determined using data whenever possible, otherwise simulation is used, with the events weighted to match the relevant distributions in data The pp collisions are generated using Pythia 6.4 [15] with a specific LHCb configuration [16] Hadron decays are described by EvtGen [17] in which final state radiation is generated using Photos [18] The interaction of the generated particles with the detector and its response are implemented using the Geant4 toolkit [19, 20] as described in ref [21] –4– JHEP05(2013)159 information is used to distinguish charged pions from kaons [22] The difference between the logarithms of the likelihoods of the kaon and pion hypotheses is required to be larger than for kaons and smaller than for pions; the combined efficiency of these cuts is 88% Candidates with a K + π − invariant mass within 130 MeV/c2 of the nominal K ∗0 mass and a good quality vertex fit are retained for further analysis To remove background from Bs0 → J/ψ (e+ e− )φ and Bs0 → φe+ e− decays, where one of the kaons is misidentified as a pion, the mass computed under the K + K − hypothesis is required to be larger than 1040 MeV/c2 Bremsstrahlung radiation, if not accounted for, would worsen the B mass resolution If the radiation occurs downstream of the dipole magnet the momentum of the electron is correctly measured and the photon energy is deposited in the same calorimeter cell as the electron In contrast, if photons are emitted upstream of the magnet, the measured electron momentum will be that after photon emission, and the measured B mass will be degraded In general, these bremsstrahlung photons will deposit their energy in different calorimeter cells than the electron In both cases, the ratio of the energy detected in the ECAL to the momentum measured by the tracking system, an important variable in identifying electrons, is unbiased To improve the momentum reconstruction, a dedicated bremsstrahlung recovery procedure is used, correcting the measured electron momentum by the bremsstrahlung photon energy As there is little material within the magnet, the bremsstrahlung photons are searched for among neutral clusters with an energy larger than 75 MeV in a well defined position given by the electron track extrapolation from before the magnet Oppositely-charged electron pairs with an electron pT larger than 350 MeV/c and a good quality vertex are used to form B → K ∗0 e+ e− and B → J/ψ (e+ e− )K ∗0 candidates The e+ e− invariant mass is required to be in the range 30–1000 MeV/c2 or 2400–3400 MeV/c2 for the two decay modes, respectively Candidate K ∗0 mesons and e+ e− pairs are combined to form B candidates which are required to have a good-quality vertex For each B candidate, the production vertex is assigned to be that with the smallest IP χ2 The B candidate is also required to have a direction that is consistent with coming from the PV as well as a reconstructed decay point that is significantly separated from the PV In order to maximize the signal efficiency while still reducing the high level of combinatorial background, a multivariate analysis, based on a Boosted Decision Tree (BDT) [23, 24] with the AdaBoost algorithm [25], is used The signal training sample is B → K ∗0 e+ e− simulated data The background training sample is taken from the upper sideband (mB > 5600 MeV/c2 ) from half of the data sample The variables used in the BDT are the pT , the IP and track χ2 of the final state particles; the K ∗0 candidate invariant mass, the vertex χ2 and flight distance χ2 (from the PV) of the K ∗0 and e+ e− candidates; the B pT , its vertex χ2 , flight distance χ2 and IP χ2 , and the angle between the B momentum direction and its direction of flight from the PV A comparison of the BDT output for the data and the simulation for B → J/ψ (e+ e− )K ∗0 decays is shown in figure The candidates for this test are reconstructed using a J/ψ mass constraint and the background is statistically subtracted using the sPlot technique [26] based on a fit to the B invariant mass spectrum The agreement between data and simulation confirms a proper modelling of the relevant variables The optimal cut value on the BDT response is chosen by considering the combinatorial background yield (b) on the B → K ∗0 e+ e− invariant mass distribution outside the signal Candidates / 0.004 104 Data LHCb Simulation 103 102 10 0.85 0.9 0.95 BDT output Figure Output of the BDT for B → J/ψ (e+ e− )K ∗0 data (points) and simulation (red line) region1 and evaluating the signal yield (s) using the B → K ∗0 e+ e− simulation assuming √ a visible B → K ∗0 e+ e− branching fraction of 2.7 × 10−7 The quantity s/ s + b serves as an optimisation metric, for which the optimal BDT cut is 0.96 The signal efficiency of this cut is about 93% while the background is reduced by two orders of magnitude After applying the BDT selection, specific backgrounds from decays that have the same visible final state particles as the B → K ∗0 e+ e− signal remain Since some of these backgrounds have larger branching fractions, additional requirements are applied to the B → K ∗0 e+ e− and B → J/ψ (e+ e− )K ∗0 candidates A large non-peaking background comes from the B → D− e+ ν decay, with D− → e− νK ∗0 The branching fraction for this channel is about five orders of magnitude larger than that of the signal When the neutrinos have low energies, the signal selections are ineffective at rejecting this background Therefore, the K ∗0 e− invariant mass is required to be larger than 1900 MeV/c2 , which is 97% efficient on signal decays Another important source of background comes from the B → K ∗0 γ decay, where the photon converts into an e+ e− pair In LHCb, approximately 40% of the photons convert before the calorimeter, and although only about 10% are reconstructed as an e+ e− pair, the resulting mass of the B candidate peaks in the signal region This background is suppressed by a factor 23 after the selection cuts (including the 30 MeV/c2 minimum requirement on the e+ e− invariant mass) The fact that signal e+ e− pairs are produced at the B decay point, whereas conversion electrons are produced in the VELO detector material, is exploited to further suppress this background The difference in the z coordinates, ∆z, between the first VELO hit and the expected position of the first hit, assuming the electron was produced at the K ∗0 vertex, should satisfy |∆z| < 30 mm In addition, we require that the calculated uncertainty on the z-position of the e+ e− vertex be less than 30 mm, since a large uncertainty makes it difficult to determine if the e+ e− pair originates from the same vertex as the K ∗0 The signal region is defined as ±300 MeV/c2 around the nominal B mass –5– JHEP05(2013)159 0.8 Fitting procedure Since the signal resolution, type and rate of backgrounds depend on whether the hardware trigger was caused by a signal electron or by other activity in the event, the data sample is divided into two mutually exclusive categories: events triggered by an extra particle (e, γ, h, µ) excluding the four final state particles (called HWTIS, since they are triggered independently of the signal) and events for which one of the electrons from the B decay satisfies the hardware electron trigger (HWElectron) Events satisfying both requirements (20%) are assigned to the HWTIS category The numbers of reconstructed signal candidates are determined from unbinned maximum likelihood fits to their mass distributions separately for each trigger category The mass distribution of each category is fitted to a sum of probability density functions (PDFs) modelling the different components The signal is described by the sum of two Crystal Ball functions [27] (CB) sharing all their parameters but with different widths The combinatorial background is described by an exponential function The shapes of the partially reconstructed hadronic and J/ψ backgrounds are described by non-parametric PDFs [28] determined from fully simulated events The signal shape parameters are fixed to the values obtained from simulation, unless otherwise specified There are seven free parameters for the B → J/ψ (e+ e− )K ∗0 fit for each trigger category These include the peak value of the B candidate mass, a scaling factor applied to the widths of the CB functions to take into account small differences between simulation –6– JHEP05(2013)159 meson, or from a point inside the detector material These two additional requirements reject about 2/3 of the remaining B → K ∗0 γ background, while retaining about 90% of the B → K ∗0 e+ e− signal After applying these cuts, the B → K ∗0 γ contamination under the B → K ∗0 e+ e− signal peak is estimated to be (10 ± 3)% of the expected signal yield Other specific backgrounds have been studied using either simulated data or analytical calculations and include the decays B → K ∗ η, K ∗ η , K ∗ π and Λ0b → Λ∗ γ, where Λ∗ represents a high mass resonance decaying into a proton and a charged kaon The main source of background is found to be the B → K ∗ η mode, followed by a Dalitz decay (η → γe+ e− ) These events form an almost flat background in the mass range 4300 − 5250 MeV/c2 None of these backgrounds contribute significantly in the B mass region, and therefore are not specifically modelled in the mass fits described later More generally, partially reconstructed backgrounds arise from B decays with one or more decay products in addition to a K ∗0 meson and an e+ e− pair In the case of the B → J/ψ (e+ e− )K ∗0 decay, there are two sources for these partially reconstructed events: those from the hadronic part, such as events with higher K ∗ resonances (partially reconstructed hadronic background), and those from the J/ψ part (partially reconstructed J/ψ background), such as events coming from ψ(2S) decays For the B → K ∗0 e+ e− decay mode, only the partially reconstructed hadronic background has to be considered Candidates / (50 MeV/ c 2) Candidates / (50 MeV/ c 2) LHCb HWElectron 1000 800 600 400 200 800 LHCb HWTIS 700 600 500 400 300 200 100 4500 5000 5500 6000 m( e e K * 0) 4500 5000 5500 6000 m( e+e− K * 0) [MeV / c 2] [MeV / c ] Figure Invariant mass distributions for the B → J/ψ (e+ e− )K ∗0 decay mode for the (left) HWElectron and (right) HWTIS trigger categories The dashed line is the signal PDF, the light grey area corresponds to the combinatorial background, the medium grey area is the partially reconstructed hadronic background and the dark grey area is the partially reconstructed J/ψ background component Trigger category HWElectron HWTIS B → J/ψ (e+ e− )K ∗0 B → K ∗0 e+ e− 4305 ± 101 14.1 +7.0 −6.3 5082 ± 104 15.0 +5.1 −4.5 Table Signal yields with their statistical uncertainties and data, and the exponent of the combinatorial background The remaining four free parameters are the yields for each fit component The invariant mass distributions together with the PDFs resulting from the fit are shown in figure The number of signal events in each category is summarized in table A fit to the B → K ∗0 e+ e− candidates is then performed, with several parameters fixed to the values found from the B → J/ψ (e+ e− )K ∗0 fit These fixed parameters are the scaling factor applied to the widths of the CB functions, the peak value of the B candidate mass and the ratio of the partially reconstructed hadronic background to the signal yield The B → K ∗0 γ yield is fixed in the B → K ∗0 e+ e− mass fit using the fitted B → J/ψ (e+ e− )K ∗0 signal yield, the ratio of efficiencies of the B → K ∗0 γ and B → J/ψ (e+ e− )K ∗0 modes, and the ratio of branching fractions B(B → K ∗0 γ)/B(B → J/ψ (e+ e− )K ∗0 ) Hence there are three free parameters for the B → K ∗0 e+ e− fit for each trigger category: the exponent and yield of the combinatorial background and the signal yield The invariant mass distributions together with the PDFs resulting from the fit are shown in figure The signal yield in each trigger category is summarized in table The probability of the background fluctuating to obtain the observed signal corresponds to 4.1 standard deviations for the HWElectron category and 2.4 standard deviations for the HWTIS category, as determined from the change in the value of twice the natural logarithm of the likelihood of the fit with and without signal Combining the two results, the statistical significance of the signal corresponds to 4.8 standard deviations –7– JHEP05(2013)159 + − Candidates / (50 MeV/ c 2) Candidates / (50 MeV/ c 2) LHCb HWElectron 12 10 LHCb HWTIS 12 10 4500 5000 5500 6000 m( e e K * 0) 4500 5000 5500 6000 m( e+e− K * 0) [MeV / c 2] [MeV / c ] Figure Invariant mass distributions for the B → K ∗0 e+ e− decay mode for the (left) HWElectron and (right) HWTIS trigger categories The dashed line is the signal PDF, the light grey area corresponds to the combinatorial background, the medium grey area is the partially reconstructed hadronic background and the black area is the B → K ∗0 γ component rsel rPID rHW HWElectron category HWTIS category 1.03 ± 0.02 1.03 ± 0.02 1.01 ± 0.02 1.35 ± 0.03 1.03 ± 0.02 Table Ratios of efficiencies used for the measurement of the B → K ∗0 e+ e− branching fraction The ratio rHW for the HWTIS trigger category is assumed to be equal to unity The uncertainties are the total ones and are discussed in section Results The B → K ∗0 e+ e− branching fraction is calculated in each trigger category using the measured signal yields and the ratio of efficiencies B(B → K ∗0 e+ e− )30−1000 MeV/c = N (B 0→K ∗0 e+ e− ) × rsel × rPID × rHW N (B 0→J/ψ (e+ e− )K ∗0 ) ×B(B → J/ψ K ∗0 ) × B(J/ψ → e+ e− ), (5.1) where the ratio of efficiencies is sub-divided into the contributions arising from the selection requirements (including acceptance effects, but excluding PID), rsel , the PID requirements rPID and the trigger requirements rHW The values of rsel are determined using simulated data, while rPID and rHW are obtained directly from calibration data samples: J/ψ → e+ e− and D0 → K − π + from D∗+ decays for rPID and B → J/ψ (e+ e− )K ∗0 decays for rHW The values are summarized in table The only ratio that is inconsistent with unity is the hardware trigger efficiency due to the different mean electron pT for the B → K ∗0 e+ e− and B → J/ψ (e+ e− )K ∗0 decays The branching fraction for the B → J/ψ K ∗0 decay mode is taken from ref [14] and a correction factor of 1.02 has been applied to take into account the difference in the Kπ invariant mass range used, and therefore the different S-wave contributions –8– JHEP05(2013)159 + − The B → K ∗0 e+ e− branching fraction, for each trigger category, is measured to be 30−1000 MeV/c2 B(B → K ∗0 e+ e− )HWElectron 30−1000 MeV/c2 B(B → K ∗0 e+ e− )HWTIS −7 = (3.3 +1.1 −1.0 ) × 10 −7 = (2.8 +1.4 −1.2 ) × 10 , where the uncertainties are statistical only Systematic uncertainties –9– JHEP05(2013)159 Several sources of systematic uncertainty are considered, affecting either the determination of the number of signal events or the computation of the efficiencies They are summarized in table The ratio of trigger efficiencies is determined using a B → J/ψ (e+ e− )K ∗0 calibration sample from data, which is reweighted using the pT of the triggering electron in order to model properly the kinematical properties of the two decays The uncertainties due to the limited size of the calibration samples are propagated to get the related systematic uncertainty shown in table The PID calibration introduces a systematic uncertainty on the calculated PID efficiencies as given in table For the kaon and pion candidates this systematic uncertainty is estimated by comparing, in simulated events, the results obtained using a D∗+ calibration sample to the true simulated PID performance For the e+ e− candidates, the systematic uncertainty is assessed ignoring the pT dependence of the electron identification The resulting effect is limited by the fact that the kinematic differences between the B → J/ψ (e+ e− )K ∗0 and the B → K ∗0 e+ e− decays are small once the full selection chain is applied The fit procedure is validated with pseudo-experiments Samples are generated with different fractions or shapes for the partially reconstructed hadronic background, or different values for the fixed signal parameters and are then fitted with the standard PDFs The corresponding systematic uncertainty is estimated from the bias in the results obtained by performing the fits described above The resulting deviations from zero of each variation are added in quadrature to get the total systematic uncertainty due to the fitting procedure The parameters of the signal shape are varied within their statistical uncertainties as obtained from the B → J/ψ (e+ e− )K ∗0 fit An alternate signal shape, obtained by studying B → J/ψ (e+ e− )K ∗0 signal decays in data both with and without a J/ψ mass constraint is also tried; the difference in the yields from that obtained using the nominal signal shape is taken as an additional source of uncertainty The ratio of the partially reconstructed hadronic background to the signal yield is assumed to be identical to that determined from the B → J/ψ (e+ e− )K ∗0 fit The systematic uncertainty linked to this hypothesis is evaluated by varying the ratio by ±50% The fraction of partially reconstructed hadronic background thus determined is in agreement within errors with the one found in B → K ∗0 γ decays [29] The shape of the partially reconstructed background used in the B → J/ψ (e+ e− )K ∗0 and the B → K ∗0 e+ e− fits are the same The related systematic uncertainty has been evaluated using an alternative shape obtained from charmless b-hadron decays The B → K ∗0 γ contamination in the B → K ∗0 e+ e− signal sample is 1.2±0.4 and Source HWElectron category HWTIS category Simulation sample statistics 0.06 0.05 Trigger efficiency 0.07 - PID efficiency 0.08 0.10 Fit procedure +0.09 −0.22 +0.07 −0.23 B → K ∗0 γ contamination 0.08 0.08 +0.17 −0.26 +0.16 −0.27 Total 1.5 ± 0.5 events for the HWElectron and HWTIS signal samples, respectively Combining the systematic uncertainties in quadrature, the branching fractions are found to be 30−1000 MeV/c2 = (3.3 +1.1 −1.0 +0.2 −0.3 30−1000 MeV/c2 = (2.8 +1.4 −1.2 +0.2 −0.3 B(B → K ∗0 e+ e− )HWElectron B(B → K ∗0 e+ e− )HWTIS ± 0.2) × 10−7 ± 0.2) × 10−7 , where the first error is statistical, the second systematic, and the third comes from the uncertainties on the B → J/ψ K ∗0 and J/ψ → e+ e− branching fractions [13, 14] The branching ratios are combined assuming all the systematic uncertainties to be fully correlated between the two trigger categories except those related to the size of the simulation samples The combined branching ratio is found to be B(B → K ∗0 e+ e− )30−1000 MeV/c = (3.1 +0.9 −0.8 +0.2 −0.3 ± 0.2) × 10−7 Summary Using pp collision data corresponding to an integrated luminosity of 1.0 fb−1 , collected by the LHCb experiment in 2011 at a centre-of-mass energy of TeV, a sample of approximately 30 B → K ∗0 e+ e− events, in the dilepton mass range 30 to 1000 MeV/c2 , has been observed The probability of the background to fluctuate upward to form the signal corresponds to 4.6 standard deviations including systematic uncertainties The B → J/ψ (e+ e− )K ∗0 decay mode is utilized as a normalization channel, and the branching fraction B(B → K ∗0 e+ e− ) is measured to be B(B → K ∗0 e+ e− )30−1000 MeV/c = (3.1 +0.9 −0.8 +0.2 −0.3 ± 0.2) × 10−7 This result can be compared to theoretical predictions A simplified formula suggested in ref [5] takes into account only the photon diagrams of figure When evaluated in the 30 to 1000 MeV/c2 e+ e− invariant mass interval using B(B → K ∗0 γ) [1–3], it predicts a B → K ∗0 e+ e− branching fraction of 2.35 × 10−7 A full calculation has been recently performed [30] and the numerical result for the e+ e− invariant mass interval of interest −7 is (2.43+0.66 −0.47 ) × 10 The consistency between the two values reflects the photon pole dominance The result presented here is in good agreement with both predictions – 10 – JHEP05(2013)159 Table Absolute systematic uncertainties on the B → K ∗0 e+ e− branching ratio (in 10−7 ) Using the full LHCb data sample obtained in 2011–2012 it will be possible to an angular analysis The measurement of the A2T parameter [8] thus obtained, is sensitive to the existence of right handed currents in the virtual loops in diagrams similar to those of figure For this purpose, the analysis of the B → K ∗0 e+ e− decay is complementary to that of the B → K ∗0 µ+ µ− mode Indeed, it is predominantly sensitive to a modification of C7 (the so-called C7 terms) while, because of the higher q in the decay, the B → K ∗0 µ+ µ− A2T parameter has a larger possible contribution from the C9 terms [31] We express our gratitude to our colleagues in the CERN accelerator departments for the excellent performance of the LHC We thank the technical and administrative staff at the LHCb institutes We acknowledge support from CERN and from the national agencies: CAPES, CNPq, FAPERJ and FINEP (Brazil); NSFC (China); CNRS/IN2P3 and Region Auvergne (France); BMBF, DFG, HGF and MPG (Germany); SFI (Ireland); INFN (Italy); FOM and NWO (The Netherlands); SCSR (Poland); ANCS/IFA (Romania); MinES, Rosatom, RFBR and NRC “Kurchatov Institute” (Russia); MinECo, XuntaGal and GENCAT (Spain); SNSF and SER (Switzerland); NAS Ukraine (Ukraine); STFC (United Kingdom); NSF (U.S.A.) We also acknowledge the support received from the ERC under FP7 The Tier1 computing centres are supported by IN2P3 (France), KIT and BMBF (Germany), INFN (Italy), NWO and SURF (The Netherlands), PIC (Spain), GridPP (United Kingdom) We are thankful for the computing resources put at our disposal by Yandex LLC (Russia), as well as to the communities behind the multiple open source software packages that we depend on Open Access This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited References [1] BaBar collaboration, B Aubert et al., Measurement of branching fractions and CP and isospin asymmetries in B → K ∗ (892)γ decays, Phys Rev Lett 103 (2009) 211802 [arXiv:0906.2177] [INSPIRE] [2] BELLE collaboration, M Nakao et al., Measurement of the B → K ∗ γ branching fractions and asymmetries, Phys Rev D 69 (2004) 112001 [hep-ex/0402042] [INSPIRE] [3] CLEO collaboration, T Coan et al., Study of exclusive radiative B meson decays, Phys Rev Lett 84 (2000) 5283 [hep-ex/9912057] [INSPIRE] [4] A Ali, B.D Pecjak and C Greub, B → V γ decays at NNLO in SCET, Eur Phys J C 55 (2008) 577 [arXiv:0709.4422] [INSPIRE] [5] Y Grossman and D Pirjol, Extracting and using photon polarization information in radiative B decays, JHEP 06 (2000) 029 [hep-ph/0005069] [INSPIRE] – 11 – JHEP05(2013)159 Acknowledgments [6] A.Y Korchin and V.A Kovalchuk, Contribution of low-lying vector resonances to ¯0 → K ¯ ∗0 e+ e− decay, Phys Rev D 82 (2010) 034013 polarization observables in B d [arXiv:1004.3647] [INSPIRE] [7] LHCb collaboration, Differential branching fraction and angular analysis of the decay B → K ∗0 µ+ µ− , Phys Rev Lett 108 (2012) 181806 [arXiv:1112.3515] [INSPIRE] [8] F Kră uger and J Matias, Probing new physics via the transverse amplitudes of B → K ∗0 (→ K − π + ) + − at large recoil, Phys Rev D 71 (2005) 094009 [hep-ph/0502060] [INSPIRE] [10] BELLE collaboration, J.-T Wei et al., Measurement of the differential branching fraction and forward-backword asymmetry for B → K (∗) + − , Phys Rev Lett 103 (2009) 171801 [arXiv:0904.0770] [INSPIRE] [11] LHCb collaboration, The LHCb detector at the LHC, 2008 JINST S08005 [INSPIRE] [12] R Aaij et al., The LHCb trigger and its performance in 2011, 2013 JINST P04022 [arXiv:1211.3055] [INSPIRE] [13] Particle Data Group collaboration, J Beringer et al., Review of particle physics (RPP), Phys Rev D 86 (2012) 010001 [INSPIRE] [14] BaBar collaboration, B Aubert et al., Measurement of branching fractions and charge asymmetries for exclusive B decays to charmonium, Phys Rev Lett 94 (2005) 141801 [hep-ex/0412062] [INSPIRE] [15] T Sjă ostrand, S Mrenna and P.Z Skands, PYTHIA 6.4 physics and manual, JHEP 05 (2006) 026 [hep-ph/0603175] [INSPIRE] [16] I Belyaev et al., Handling of the generation of primary events in Gauss, the LHCb simulation framework, IEEE Nucl Sci Symp Conf Rec (2010) 1155 [17] D Lange, The EvtGen particle decay simulation package, Nucl Instrum Meth A 462 (2001) 152 [INSPIRE] [18] P Golonka and Z Was, PHOTOS Monte Carlo: a precision tool for QED corrections in Z and W decays, Eur Phys J C 45 (2006) 97 [hep-ph/0506026] [INSPIRE] [19] GEANT4 collaboration, J Allison et al., GEANT4 developments and applications, IEEE Trans Nucl Sci 53 (2006) 270 [20] GEANT4 collaboration, S Agostinelli et al., GEANT4: a simulation toolkit, Nucl Instrum Meth A 506 (2003) 250 [INSPIRE] [21] M Clemencic et al., The LHCb simulation application, Gauss: design, evolution and experience, J Phys Conf Ser 331 (2011) 032023 [22] M Adinolfi et al., Performance of the LHCb RICH detector at the LHC, submitted to Eur Phys J C [arXiv:1211.6759] [INSPIRE] [23] L Breiman, J.H Friedman, R.A Olshen and C.J Stone, Classification and regression trees, Wadsworth international group, Belmont U.S.A (1984) [24] B.P Roe et al., Boosted decision trees, an alternative to artificial neural networks, Nucl Instrum Meth A 543 (2005) 577 [physics/0408124] [INSPIRE] – 12 – JHEP05(2013)159 [9] BaBar collaboration, J Lees et al., Measurement of branching fractions and rate asymmetries in the rare decays B → K (∗) + − , Phys Rev D 86 (2012) 032012 [arXiv:1204.3933] [INSPIRE] [25] R.E Schapire and Y Freund, A decision-theoretic generalization of on-line learning and an application to boosting, J Comput Syst Sci 55 (1997) 119 [26] M Pivk and F.R Le Diberder, SPlot: a statistical tool to unfold data distributions, Nucl Instrum Meth A 555 (2005) 356 [physics/0402083] [INSPIRE] [27] T Skwarnicki, A study of the radiative cascade transitions between the Υ and Υ resonances, Ph.D thesis, Institute of Nuclear Physics, Krakow Poland (1986) [28] K.S Cranmer, Kernel estimation in high-energy physics, Comput Phys Commun 136 (2001) 198 [hep-ex/0011057] [INSPIRE] [30] S Jager and J.M Camalich, On B → V at small dilepton invariant mass, power corrections and new physics, JHEP 05 (2013) 043 [arXiv:1212.2263] [INSPIRE] [31] D Becirevic and E Schneider, On transverse asymmetries in B → K ∗ 854 (2012) 321 [arXiv:1106.3283] [INSPIRE] – 13 – + − , Nucl Phys B JHEP05(2013)159 [29] LHCb collaboration, Measurement of the ratio of branching fractions BR(B → K ∗0 γ)/BR(Bs0 → φγ) and the direct CP asymmetry in B → K ∗0 γ , Nucl Phys B 867 (2013) [arXiv:1209.0313] [INSPIRE] The LHCb collaboration – 14 – JHEP05(2013)159 R Aaij40 , C Abellan Beteta35,n , B Adeva36 , M Adinolfi45 , C Adrover6 , A Affolder51 , Z Ajaltouni5 , J Albrecht9 , F Alessio37 , M Alexander50 , S Ali40 , G Alkhazov29 , P Alvarez Cartelle36 , A.A Alves Jr24,37 , S Amato2 , S Amerio21 , Y Amhis7 , L Anderlini17,f , J Anderson39 , R Andreassen56 , R.B Appleby53 , O Aquines Gutierrez10 , F Archilli18 , A Artamonov 34 , M Artuso57 , E Aslanides6 , G Auriemma24,m , S Bachmann11 , J.J Back47 , C Baesso58 , V Balagura30 , W Baldini16 , R.J Barlow53 , C Barschel37 , S Barsuk7 , W Barter46 , Th Bauer40 , A Bay38 , J Beddow50 , F Bedeschi22 , I Bediaga1 , S Belogurov30 , K Belous34 , I Belyaev30 , E Ben-Haim8 , M Benayoun8 , G Bencivenni18 , S Benson49 , J Benton45 , A Berezhnoy31 , R Bernet39 , M.-O Bettler46 , M van Beuzekom40 , A Bien11 , S Bifani44 , T Bird53 , A Bizzeti17,h , P.M Bjørnstad53 , T Blake37 , F Blanc38 , J Blouw11 , S Blusk57 , V Bocci24 , A Bondar33 , N Bondar29 , W Bonivento15 , S Borghi53 , A Borgia57 , T.J.V Bowcock51 , E Bowen39 , C Bozzi16 , T Brambach9 , J van den Brand41 , J Bressieux38 , D Brett53 , M Britsch10 , T Britton57 , N.H Brook45 , H Brown51 , I Burducea28 , A Bursche39 , G Busetto21,q , J Buytaert37 , S Cadeddu15 , O Callot7 , M Calvi20,j , M Calvo Gomez35,n , A Camboni35 , P Campana18,37 , D Campora Perez37 , A Carbone14,c , G Carboni23,k , R Cardinale19,i , A Cardini15 , H Carranza-Mejia49 , L Carson52 , K Carvalho Akiba2 , G Casse51 , M Cattaneo37 , Ch Cauet9 , M Charles54 , Ph Charpentier37 , P Chen3,38 , N Chiapolini39 , M Chrzaszcz 25 , K Ciba37 , X Cid Vidal37 , G Ciezarek52 , P.E.L Clarke49 , M Clemencic37 , H.V Cliff46 , J Closier37 , C Coca28 , V Coco40 , J Cogan6 , E Cogneras5 , P Collins37 , A Comerma-Montells35 , A Contu15,37 , A Cook45 , M Coombes45 , S Coquereau8 , G Corti37 , B Couturier37 , G.A Cowan49 , D.C Craik47 , S Cunliffe52 , R Currie49 , C D’Ambrosio37 , P David8 , P.N.Y David40 , I De Bonis4 , K De Bruyn40 , S De Capua53 , M De Cian39 , J.M De Miranda1 , L De Paula2 , W De Silva56 , P De Simone18 , D Decamp4 , M Deckenhoff9 , L Del Buono8 , D Derkach14 , O Deschamps5 , F Dettori41 , A Di Canto11 , H Dijkstra37 , M Dogaru28 , S Donleavy51 , F Dordei11 , A Dosil Su´arez36 , D Dossett47 , A Dovbnya42 , F Dupertuis38 , R Dzhelyadin34 , A Dziurda25 , A Dzyuba29 , S Easo48,37 , U Egede52 , V Egorychev30 , S Eidelman33 , D van Eijk40 , S Eisenhardt49 , U Eitschberger9 , R Ekelhof9 , L Eklund50,37 , I El Rifai5 , Ch Elsasser39 , D Elsby44 , A Falabella14,e , C Făarber11 , G Fardell49 , C Farinelli40 , S Farry12 , V Fave38 , D Ferguson49 , V Fernandez Albor36 , F Ferreira Rodrigues1 , M Ferro-Luzzi37 , S Filippov32 , M Fiore16 , C Fitzpatrick37 , M Fontana10 , F Fontanelli19,i , R Forty37 , O Francisco2 , M Frank37 , C Frei37 , M Frosini17,f , S Furcas20 , E Furfaro23,k , A Gallas Torreira36 , D Galli14,c , M Gandelman2 , P Gandini57 , Y Gao3 , J Garofoli57 , P Garosi53 , J Garra Tico46 , L Garrido35 , C Gaspar37 , R Gauld54 , E Gersabeck11 , M Gersabeck53 , T Gershon47,37 , Ph Ghez4 , V Gibson46 , V.V Gligorov37 , C Găobel58 , D Golubkov30 , A Golutvin52,30,37 , A Gomes2 , H Gordon54 , M Grabalosa G´andara5 , R Graciani Diaz35 , L.A Granado Cardoso37 , E Graug´es35 , G Graziani17 , A Grecu28 , E Greening54 , S Gregson46 , O Gră unberg59 , B Gui57 , E Gushchin32 , Yu Guz34,37 , T Gys37 , C Hadjivasiliou57 , G Haefeli38 , C Haen37 , S.C Haines46 , S Hall52 , T Hampson45 , S Hansmann-Menzemer11 , N Harnew54 , S.T Harnew45 , J Harrison53 , T Hartmann59 , J He37 , V Heijne40 , K Hennessy51 , P Henrard5 , J.A Hernando Morata36 , E van Herwijnen37 , E Hicks51 , D Hill54 , M Hoballah5 , C Hombach53 , P Hopchev4 , W Hulsbergen40 , P Hunt54 , T Huse51 , N Hussain54 , D Hutchcroft51 , D Hynds50 , V Iakovenko43 , M Idzik26 , P Ilten12 , R Jacobsson37 , A Jaeger11 , E Jans40 , P Jaton38 , F Jing3 , M John54 , D Johnson54 , C.R Jones46 , B Jost37 , M Kaballo9 , S Kandybei42 , M Karacson37 , T.M Karbach37 , I.R Kenyon44 , U Kerzel37 , T Ketel41 , A Keune38 , B Khanji20 , O Kochebina7 , I Komarov38 , R.F Koopman41 , P Koppenburg40 , M Korolev31 , A Kozlinskiy40 , L Kravchuk32 , K Kreplin11 , – 15 – JHEP05(2013)159 M Kreps47 , G Krocker11 , P Krokovny33 , F Kruse9 , M Kucharczyk20,25,j , V Kudryavtsev33 , T Kvaratskheliya30,37 , V.N La Thi38 , D Lacarrere37 , G Lafferty53 , A Lai15 , D Lambert49 , R.W Lambert41 , E Lanciotti37 , G Lanfranchi18 , C Langenbruch37 , T Latham47 , C Lazzeroni44 , R Le Gac6 , J van Leerdam40 , J.-P Lees4 , R Lef`evre5 , A Leflat31 , J Lefran¸cois7 , S Leo22 , O Leroy6 , T Lesiak25 , B Leverington11 , Y Li3 , L Li Gioi5 , M Liles51 , R Lindner37 , C Linn11 , B Liu3 , G Liu37 , S Lohn37 , I Longstaff50 , J.H Lopes2 , E Lopez Asamar35 , N Lopez-March38 , H Lu3 , D Lucchesi21,q , J Luisier38 , H Luo49 , F Machefert7 , I.V Machikhiliyan4,30 , F Maciuc28 , O Maev29,37 , S Malde54 , G Manca15,d , G Mancinelli6 , U Marconi14 , R Mă arki38 , J Marks11 , G Martellotti24 , A Martens8 , L Martin54 , A Mart´ın S´ anchez , M Martinelli40 , D Martinez Santos41 , D Martins Tostes2 , A Massafferri1 , 37 R Matev , Z Mathe37 , C Matteuzzi20 , E Maurice6 , A Mazurov16,32,37,e , J McCarthy44 , R McNulty12 , A Mcnab53 , B Meadows56,54 , F Meier9 , M Meissner11 , M Merk40 , D.A Milanes8 , M.-N Minard4 , J Molina Rodriguez58 , S Monteil5 , D Moran53 , P Morawski25 , M.J Morello22,s , R Mountain57 , I Mous40 , F Muheim49 , K Mă uller39 , R Muresan28 , 26 38 45 38 B Muryn , B Muster , P Naik , T Nakada , R Nandakumar48 , I Nasteva1 , M Needham49 , N Neufeld37 , A.D Nguyen38 , T.D Nguyen38 , C Nguyen-Mau38,p , M Nicol7 , V Niess5 , R Niet9 , N Nikitin31 , T Nikodem11 , A Nomerotski54 , A Novoselov34 , A Oblakowska-Mucha26 , V Obraztsov34 , S Oggero40 , S Ogilvy50 , O Okhrimenko43 , R Oldeman15,d , M Orlandea28 , J.M Otalora Goicochea2 , P Owen52 , A Oyanguren 35,o , B.K Pal57 , A Palano13,b , M Palutan18 , J Panman37 , A Papanestis48 , M Pappagallo50 , C Parkes53 , C.J Parkinson52 , G Passaleva17 , G.D Patel51 , M Patel52 , G.N Patrick48 , C Patrignani19,i , C Pavel-Nicorescu28 , A Pazos Alvarez36 , A Pellegrino40 , G Penso24,l , M Pepe Altarelli37 , S Perazzini14,c , D.L Perego20,j , E Perez Trigo36 , A P´erez-Calero Yzquierdo35 , P Perret5 , M Perrin-Terrin6 , G Pessina20 , K Petridis52 , A Petrolini19,i , A Phan57 , E Picatoste Olloqui35 , B Pietrzyk4 , T Pilaˇr47 , D Pinci24 , S Playfer49 , M Plo Casasus36 , F Polci8 , G Polok25 , A Poluektov47,33 , E Polycarpo2 , D Popov10 , B Popovici28 , C Potterat35 , A Powell54 , J Prisciandaro38 , C Prouve7 , V Pugatch43 , A Puig Navarro38 , G Punzi22,r , W Qian4 , J.H Rademacker45 , B Rakotomiaramanana38 , M.S Rangel2 , I Raniuk42 , N Rauschmayr37 , G Raven41 , S Redford54 , M.M Reid47 , A.C dos Reis1 , S Ricciardi48 , A Richards52 , K Rinnert51 , V Rives Molina35 , D.A Roa Romero5 , P Robbe7 , E Rodrigues53 , P Rodriguez Perez36 , S Roiser37 , V Romanovsky34 , A Romero Vidal36 , J Rouvinet38 , T Ruf37 , F Ruffini22 , H Ruiz35 , P Ruiz Valls35,o , G Sabatino24,k , J.J Saborido Silva36 , N Sagidova29 , P Sail50 , B Saitta15,d , C Salzmann39 , B Sanmartin Sedes36 , M Sannino19,i , R Santacesaria24 , C Santamarina Rios36 , E Santovetti23,k , M Sapunov6 , A Sarti18,l , C Satriano24,m , A Satta23 , M Savrie16,e , D Savrina30,31 , P Schaack52 , M Schiller41 , H Schindler37 , M Schlupp9 , M Schmelling10 , B Schmidt37 , O Schneider38 , A Schopper37 , M.-H Schune7 , R Schwemmer37 , B Sciascia18 , A Sciubba24 , M Seco36 , A Semennikov30 , K Senderowska26 , I Sepp52 , N Serra39 , J Serrano6 , P Seyfert11 , M Shapkin34 , I Shapoval16,42 , P Shatalov30 , Y Shcheglov29 , T Shears51,37 , L Shekhtman33 , O Shevchenko42 , V Shevchenko30 , A Shires52 , R Silva Coutinho47 , T Skwarnicki57 , N.A Smith51 , E Smith54,48 , M Smith53 , M.D Sokoloff56 , F.J.P Soler50 , F Soomro18 , D Souza45 , B Souza De Paula2 , B Spaan9 , A Sparkes49 , P Spradlin50 , F Stagni37 , S Stahl11 , O Steinkamp39 , S Stoica28 , S Stone57 , B Storaci39 , M Straticiuc28 , U Straumann39 , V.K Subbiah37 , S Swientek9 , V Syropoulos41 , M Szczekowski27 , P Szczypka38,37 , T Szumlak26 , S T’Jampens4 , M Teklishyn7 , E Teodorescu28 , F Teubert37 , C Thomas54 , E Thomas37 , J van Tilburg11 , V Tisserand4 , M Tobin38 , S Tolk41 , D Tonelli37 , S Topp-Joergensen54 , N Torr54 , E Tournefier4,52 , S Tourneur38 , M.T Tran38 , M Tresch39 , A Tsaregorodtsev6 , P Tsopelas40 , N Tuning40 , M Ubeda Garcia37 , A Ukleja27 , D Urner53 , U Uwer11 , V Vagnoni14 , G Valenti14 , R Vazquez Gomez35 , P Vazquez Regueiro36 , S Vecchi16 , J.J Velthuis45 , M Veltri17,g , G Veneziano38 , M Vesterinen37 , B Viaud7 , D Vieira2 , X Vilasis-Cardona35,n , A Vollhardt39 , D Volyanskyy10 , D Voong45 , A Vorobyev29 , V Vorobyev33 , C Voß59 , H Voss10 , R Waldi59 , R Wallace12 , S Wandernoth11 , J Wang57 , D.R Ward46 , N.K Watson44 , A.D Webber53 , D Websdale52 , M Whitehead47 , J Wicht37 , J Wiechczynski25 , D Wiedner11 , L Wiggers40 , G Wilkinson54 , M.P Williams47,48 , M Williams55 , F.F Wilson48 , J Wishahi9 , M Witek25 , S.A Wotton46 , S Wright46 , S Wu3 , K Wyllie37 , Y Xie49,37 , F Xing54 , Z Xing57 , Z Yang3 , R Young49 , X Yuan3 , O Yushchenko34 , M Zangoli14 , M Zavertyaev10,a , F Zhang3 , L Zhang57 , W.C Zhang12 , Y Zhang3 , A Zhelezov11 , A Zhokhov30 , L Zhong3 and A Zvyagin37 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 Centro Brasileiro de Pesquisas F´ısicas (CBPF), Rio de Janeiro, Brazil Universidade Federal Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil Center for High Energy Physics, Tsinghua University, Beijing, China LAPP, Universit´e de Savoie, CNRS/IN2P3, Annecy-Le-Vieux, France Clermont Universit´e, Universit´e Blaise Pascal, CNRS/IN2P3, LPC, Clermont-Ferrand, France CPPM, Aix-Marseille Universit´e, CNRS/IN2P3, Marseille, France LAL, Universit´e Paris-Sud, CNRS/IN2P3, Orsay, France LPNHE, Universit´e Pierre et Marie Curie, Universit´e Paris Diderot, CNRS/IN2P3, Paris, France Fakultă at Physik, Technische Universită at Dortmund, Dortmund, Germany Max-Planck-Institut fă ur Kernphysik (MPIK), Heidelberg, Germany Physikalisches Institut, Ruprecht-Karls-Universită at Heidelberg, Heidelberg, Germany School of Physics, University College Dublin, Dublin, Ireland Sezione INFN di Bari, Bari, Italy Sezione INFN di Bologna, Bologna, Italy Sezione INFN di Cagliari, Cagliari, Italy Sezione INFN di Ferrara, Ferrara, Italy Sezione INFN di Firenze, Firenze, Italy Laboratori Nazionali dell’INFN di Frascati, Frascati, Italy Sezione INFN di Genova, Genova, Italy Sezione INFN di Milano Bicocca, Milano, Italy Sezione INFN di Padova, Padova, Italy Sezione INFN di Pisa, Pisa, Italy Sezione INFN di Roma Tor Vergata, Roma, Italy Sezione INFN di Roma La Sapienza, Roma, Italy Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Krak´ ow, Poland AGH - University of Science and Technology, Faculty of Physics and Applied Computer Science, Krak´ ow, Poland National Center for Nuclear Research (NCBJ), Warsaw, Poland Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow, Russia Institute for Nuclear Research of the Russian Academy of Sciences (INR RAN), Moscow, Russia Budker Institute of Nuclear Physics (SB RAS) and Novosibirsk State University, Novosibirsk, Russia Institute for High Energy Physics (IHEP), Protvino, Russia Universitat de Barcelona, Barcelona, Spain Universidad de Santiago de Compostela, Santiago de Compostela, Spain European Organization for Nuclear Research (CERN), Geneva, Switzerland Ecole Polytechnique F´ed´erale de Lausanne (EPFL), Lausanne, Switzerland Physik-Institut, Universită at Ză urich, Ză urich, Switzerland – 16 – JHEP05(2013)159 40 41 42 43 44 45 46 47 48 49 51 52 53 54 55 56 57 58 59 a b c d e f g h i j k l m n o p q r s P.N Lebedev Physical Institute, Russian Academy of Science (LPI RAS), Moscow, Russia Universit` a di Bari, Bari, Italy Universit` a di Bologna, Bologna, Italy Universit` a di Cagliari, Cagliari, Italy Universit` a di Ferrara, Ferrara, Italy Universit` a di Firenze, Firenze, Italy Universit` a di Urbino, Urbino, Italy Universit` a di Modena e Reggio Emilia, Modena, Italy Universit` a di Genova, Genova, Italy Universit` a di Milano Bicocca, Milano, Italy Universit` a di Roma Tor Vergata, Roma, Italy Universit` a di Roma La Sapienza, Roma, Italy Universit` a della Basilicata, Potenza, Italy LIFAELS, La Salle, Universitat Ramon Llull, Barcelona, Spain IFIC, Universitat de Valencia-CSIC, Valencia, Spain Hanoi University of Science, Hanoi, Viet Nam Universit` a di Padova, Padova, Italy Universit` a di Pisa, Pisa, Italy Scuola Normale Superiore, Pisa, Italy – 17 – JHEP05(2013)159 50 Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, The Netherlands NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine University of Birmingham, Birmingham, United Kingdom H.H Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom Department of Physics, University of Warwick, Coventry, United Kingdom STFC Rutherford Appleton Laboratory, Didcot, United Kingdom School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom Imperial College London, London, United Kingdom School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom Department of Physics, University of Oxford, Oxford, United Kingdom Massachusetts Institute of Technology, Cambridge, MA, United States University of Cincinnati, Cincinnati, OH, United States Syracuse University, Syracuse, NY, United States Pontif´ıcia Universidade Cat´ olica Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil, associated to Institut fă ur Physik, Universită at Rostock, Rostock, Germany, associated to 11 ... of the data sample The variables used in the BDT are the pT , the IP and track χ2 of the final state particles; the K ∗0 candidate invariant mass, the vertex χ2 and flight distance χ2 (from the. .. to the values found from the B → J/ψ (e+ e− )K ∗0 fit These fixed parameters are the scaling factor applied to the widths of the CB functions, the peak value of the B candidate mass and the ratio... deviations for the HWTIS category, as determined from the change in the value of twice the natural logarithm of the likelihood of the fit with and without signal Combining the two results, the